|Publication number||US7417788 B2|
|Application number||US 11/601,894|
|Publication date||Aug 26, 2008|
|Filing date||Nov 20, 2006|
|Priority date||Nov 21, 2005|
|Also published as||US20070115524|
|Publication number||11601894, 601894, US 7417788 B2, US 7417788B2, US-B2-7417788, US7417788 B2, US7417788B2|
|Inventors||Aditya Narendra Joshi|
|Original Assignee||Aditya Narendra Joshi|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (62), Non-Patent Citations (1), Referenced by (1), Classifications (8), Legal Events (1)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application claims the benefit of U.S. Provisional Patent Application No. 60/738,467 filed Nov. 21, 2005.
The invention relates to the use of active optical materials to perform logic operations using optical signals.
In the field of digital electronics, specific logic functions are performed by electronic circuits. These logic functions are commonly known by those skilled in the art of digital electronics. Examples of the logic functions and their electronic analogs are known as the AND gate, the NAND gate, the OR gate, the NOR gate and various other logic based circuits that can be designed to perform particular electronic functions. These functions are based on a truth table or logic table that defines the output when a set of selected input conditions are present. It is possible to design electronic circuits so that they replicate the results of these truth tables. In these designs substantial flexibility is available by manipulating the outputs of the gates with electronic changes such as the addition of a state inverter, which can be used with circuits to switch the nature of one gate to that of another gate or can otherwise be used to invert the digital state of a signal. Often these logic circuits are utilized in large numbers to make electronic computers.
The use of optically active materials, especially semiconductor lasers and optical fibers for data transmission, has led to increasing interest in optically driven circuits that can be driven directly by incoming photons carrying information. Eliminating the need to switch from an optical to an electrical signal improves the ability of networks to handle more data.
If entire computers could be built with optically driven circuits, they could also operate at higher speed. Because of this, it has been a goal in computer technology to build computers using optically based switching circuitry. It is thought that such optically based circuits will provide advantages in addition to improved computing speed and could find application in advanced computing techniques such as quantum computing.
In addition these optically based circuits would improve the performance and abilities in various other applications such as transmission networks and resistance to ElectroMagnetic Pulse (EMP), and other electromagnetic disturbances. However, there are a myriad of challenges before technologists to accomplish such advanced goals. In particular the creation of suitable optical logic circuits has challenged computer technologists giving rise to a need for improved optical switches that can operate individually or be made into logic gates or other information processing constructions.
An apparatus performs digital data manipulation of optical data carried by photons. The apparatus comprises an optically active material capable of existing in an excited state and a de-excited state which is used for switching between the two states. A source of pumping energy is used for exciting the optically active material to an excited state. At least one optical data signal source capable of changing the state of the optically active material is used, and a sense signal source for providing a sense signal to the optically active material for determining the state of the optically active material is used to deliver the sense signal to a detector. The detector detects the state of the optically active material from the sense signal.
An apparatus for optical logic gate data processing is provided. The apparatus comprises an optically active material that can be optically switched between at least two states. By using a pumping energy source the optically active material is excited. At least one optical data signal source capable of changing the state of the optically active material is used to process the data. To determine the state of the optically active material a sense signal source is used to provide a sensing signal. A detector is used to detect the state of the optically active material from the sense signal.
A method for optically manipulating digital optical data carried by photons is provided. This is accomplished by providing a pumping mechanism to excite an optically active material and by providing at least one digital optical signal at a frequency suitable to interact with an optically active material. The digital optical signal is used for switching the optically active material between excited and de-excited states. Various arrangements comprising at least one data signal source, at least one container of optically active material, at least one sensing signal source and at least one detector are used to form logic gates and to provide digital optical signal processing.
The invention pertains to the use of optically active dyes such as rhodamine, coumarin or other optically active materials to perform processing functions on optical data. The data is carried in pulses of photons of wavelengths appropriate to interact with and excite or de-excite the optically active materials.
The invention utilizes dye cells such as those made using commercially available rhodamine 6G, coumarin, other fluorescent dyes, or other optically active material. A dye cell is pumped using a laser or other suitable pump to raise the dye atoms and or molecules from a low energy state, also called a de-excited state or a ground state, to an excited state. The data pulse, also called data signal, which has a wavelength in the active region of the laser dye, then enters the dye cell. If the data pulse is high in energy, designated as 1 or High, the signal stimulates the excited optical material in the cell and depletes the number of excited species in the cell very rapidly. If the pulse strength is relatively low in energy, designated as 0 or Low, the number of species in the excited state in the optically active medium is not stimulated to de-excite rapidly, but decreases more slowly by spontaneous emission of photons. Accordingly, a High energy signal, designated as a 1, is a signal that is effective in stimulating emission from an optically active material that is in the excited state, and a Low energy signal, designated as a 0, is a signal that is much less effective in stimulating emission from an optically active material.
After the data signal has passed through the optically active medium, the sense pulse of the device, also in the active wavelength range of the dye, is allowed to enter the cell. If the number of species in the excited state is reduced to a de-excited state, due to a prior High level or 1 data pulse, the sense pulse will be absorbed by the optically active medium and will result in a Low level or 0 sense signal detection in the detector. If the number of molecules in the excited state has not been depleted, that is the optically active medium has not been de-excited, because the initial data pulse was at the Low or 0 level, the incoming sense pulse will be amplified in the cell and will emerge with High amplitude, providing a High or 1 level at the detector. This ability to invert the data pulse is utilized in this invention to perform logic functions such as NOT, and NAND.
Referring again to
As shown in
The time dependency of these signals is shown in
In yet another embodiment, as shown in
In another embodiment an OR gate can be formed using an arrangement as shown in
In each of the above embodiments alternative embodiments can be made by combining the separate sense pulse sources into one sense pulse source and utilizing beam splitters and mirrors to obtain the required number of beams. The same strategy can also be applied to the pump signals to reduce the number of individual sources that are necessary.
From another aspect using arrangements of just NOT gates and NAND gates can provide equivalent functionality to all the common electronic logic gates such as the AND, OR, NOR, and XOR gates. These arrangements can be configured in various ways and are well known by those skilled in the art.
In another embodiment the functionality required by nearly any truth table can be provided by those skilled in the art when properly arranging the set of logic gates to satisfy the requirements of that truth table.
Utilizing the invention, other types of logic gates can be fabricated. As discussed above, demonstrations of a NOT function and of a NAND function provide a wide ranging capability from a digital processing perspective. The fundamental arrangements of optical logic devices can be similar to those used in electronic circuits and computers. Using configurations of the logic gates discussed above, an optical circuit can be formed that provides nearly any desired set of digital process results satisfying nearly any truth table. Such configurations are commonly discussed in text books on digital processing techniques.
From yet another aspect, the invention can be used to process digital information coming from any digital source that is or can be converted to an optical data stream. The ability to digitally process such data streams from an optical perspective can dramatically increase the speed of systems. This is especially true in communications and, especially, in telephonic communications.
This invention has been explained with respect to the details, arrangements of components and certain specific embodiments shown in the accompanying drawings. Those skilled in the art can design larger and more complex optical devices that can perform more complex tasks without deviating from the spirit and scope of this invention. The appended claims are intended to be interpreted to cover apparatuses and methods that do not depart from the spirit and scope of this invention.
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|U.S. Classification||359/320, 359/885|
|International Classification||G02F1/29, G02B5/22|
|Cooperative Classification||G02F3/00, G06E1/00|
|European Classification||G06E1/00, G02F3/00|